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参照:
这篇文档翻译自以署名-相同方式共享 4.0 国际协议发布的http://www.sqlstyle.guide,译文以原文同样的协议发布。
你可以直接使用这些指导方针,或者fork后创建自己的版本——最重要的是选择一套方针并严格遵守它。欢迎通过提交issue或pull request来提交建议或修复bug。
为了让阅读了Joe Celko的《SQL ProgrammingStyle》的团队能更容易采用这套规则, 这套原则被设计成与该书的兼容的形式。该指南在某些领域严格一些,在另一些领域松懈一些。 当然该指南比Celko的书更简洁一些,因为Celko的书包含了一些趣闻和每一条原则后的理由。
将该文档的Markdown format格式添加到项目代码库中或将该页面的链接发送给所有项目的参与者要比传阅实体书容易得多。
Simon Holywell所著的《SQL样式指南》以署名-相同方式共享 4.0 国际协议发布,改编自http://www.sqlstyle.guide。
YYYY-MM-DD HH:MM:SS.SSSSS
)。WHERE
语句。/*
开始以*/
结束的块注释,或使用以--
开始的行注释。SELECT file_hash -- stored ssdeep hash FROM file_system WHERE file_name = '.vimrc';
/* Updating the file record after writing to the file */ UPDATE file_system SET file_modified_date = '1980-02-22 13:19:01.00000', file_size = 209732 WHERE file_name = '.vimrc';
sp_
或tbl
。SELECT first_name FROM staff;
staff
和employees
。tbl
或其他的描述性的前缀或匈牙利命名法。cars_mechanics
做表名不如使用services
。id
做表的主标识符。AS
关键字,因为这样的显示声明易于阅读。SELECT first_name AS fn FROM staff AS s1 JOIN students AS s2 ON s2.mentor_id = s1.staff_num;
SELECT SUM(s.monitor_tally) AS monitor_total FROM staff AS s;
sp_
或任何其他这样的叙述性前缀或使用匈牙利表示法。下列后缀有统一的意义,能保证SQL代码更容易被理解。在合适的时候使用正确的后缀。
_id
独一无二的标识符,如主键。_status
标识值或任何表示状态的值,比如publication_status
。_total
总和或某些值的和。_num
表示该域包含数值。_name
表示名字。_seq
包含一系列数值。_date
表示该列包含日期。_tally
计数值。_size
大小,如文件大小或服装大小。_addr
地址,有形的或无形的,如ip_addr
保留字总是大写,如SELECT
和WHERE
。
最好使用保留字的全称而不是简写,用ABSOLUTE
而不用ABS
。
当标准ANSI SQL关键字能完成相同的事情时,不要使用数据库服务器相关的关键字,这样能增强可移植性。
SELECT model_num FROM phones AS p WHERE p.release_date > '2014-09-30';
正确地使用空白字符对清晰的代码十分重要。不要把代码堆再一起或移除自然语言中的空格。
用空格使根关键字都结束在同一列上。在代码中形成一个从上到下的“川流”,这样帮助读者快速扫描代码并将关键字和实现细节分开。川流在排版时应该避免,但是对书写SQL语句是有帮助的。
(SELECT f.species_name, AVG(f.height) AS average_height, AVG(f.diameter) AS average_diameter FROM flora AS f WHERE f.species_name = 'Banksia' OR f.species_name = 'Sheoak' OR f.species_name = 'Wattle' GROUP BY f.species_name, f.observation_date) UNION ALL (SELECT b.species_name, AVG(b.height) AS average_height, AVG(b.diameter) AS average_diameter FROM botanic_garden_flora AS b WHERE b.species_name = 'Banksia' OR b.species_name = 'Sheoak' OR b.species_name = 'Wattle' GROUP BY b.species_name, b.observation_date)
注意WHERE
和FROM
等关键字,都右对齐,而真实的列名都左对齐。
注意下列情况总是加入空格:
=
),
)'
),除非单引号后面是括号、逗号或分号SELECT a.title, a.release_date, a.recording_date FROM albums AS a WHERE a.title = 'Charcoal Lane' OR a.title = 'The New Danger';
总是换行的情况:
AND
或OR
前。让所有的关键字右对齐,让所有的值左对齐,在查询语句中间留出一个空隙。这样能提高速读代码的速读。
INSERT INTO albums (title, release_date, recording_date) VALUES ('Charcoal Lane', '1990-01-01 01:01:01.00000', '1990-01-01 01:01:01.00000'), ('The New Danger', '2008-01-01 01:01:01.00000', '1990-01-01 01:01:01.00000');
UPDATE albums SET release_date = '1990-01-01 01:01:01.00000' WHERE title = 'The New Danger';
SELECT a.title, a.release_date, a.recording_date, a.production_date -- grouped dates together FROM albums AS a WHERE a.title = 'Charcoal Lane' OR a.title = 'The New Danger';
为确保SQL的可读性,一定要遵守下列规则。
Join语句应该缩进到川流的另一侧并在必要的时候添加一个换行。
SELECT r.last_name FROM riders AS r INNER JOIN bikes AS b ON r.bike_vin_num = b.vin_num AND b.engines > 2 INNER JOIN crew AS c ON r.crew_chief_last_name = c.last_name AND c.chief = 'Y';
子查询应该在川流的右侧对齐并使用其他查询相同的样式。有时候将右括号单独置于一行并同与它配对的左括号对齐是有意义的——尤其是当存在嵌套子查询的时候。
SELECT r.last_name, (SELECT MAX(YEAR(championship_date)) FROM champions AS c WHERE c.last_name = r.last_name AND c.confirmed = 'Y') AS last_championship_year FROM riders AS r WHERE r.last_name IN (SELECT c.last_name FROM champions AS c WHERE YEAR(championship_date) > '2008' AND c.confirmed = 'Y');
BETWEEN
而不是多个AND
语句。IN()
而不是多个OR
语句。CASE
表达式。CASE
语句能嵌套形成更复杂的逻辑结构。UNION
语句和临时表。如果数据库架构能够不靠这些语句运行,那么多数情况下它就不应该依靠这些语句。SELECT CASE postcode WHEN 'BN1' THEN 'Brighton' WHEN 'EH1' THEN 'Edinburgh' END AS city FROM office_locations WHERE country = 'United Kingdom' AND opening_time BETWEEN 8 AND 9 AND postcode IN ('EH1', 'BN1', 'NN1', 'KW1')
声明模式信息时维护可读代码也很重要。所以列定义的顺序和分组一定要有意义。
在CREATE
定义中,每列要缩进4个空格。
REAL
和FLOAT
类型,否则使用NUMERIC
和DECIMAL
类型。浮点数舍入误差是个麻烦。DECIMAL
那么就不要使用INTEGER
类型作为默认值。NOT NULL
声明前。约束和键是构成数据库系统的重要组成部分。它们能很快地变得难以阅读和理解,所以遵从指导方针是很重要的。
设计时应该谨慎选择构成键的列,因为键既明显影响着性能和数据完整性。
以上是定义数据库时合乎逻辑的平衡做法。当需求变更时,键也应该根据情况更新。
确定键后,就可以用约束和字值段验证来定义它们。
UNIQUE
、PRIMARY KEY
和FOREIGN KEY
之外。CREATE TABLE
语句后先定义主键。ON DELETE
排在ON UPDATE
前。NOT NULL
定义对齐到同一列。虽然这样的做法有些慢,但是能提高可读性。LIKE
和SIMILAR TO
约束来保证格式已知字符串的数据完整性。CHECK()
来防止错误的值进入数据库或被错误地转换。大部分情况下至少要确认值要大于零。CHECK()
约束应该在单独的语句中以便debug。CREATE TABLE staff ( PRIMARY KEY (staff_num), staff_num INT(5) NOT NULL, first_name VARCHAR(100) NOT NULL, pens_in_drawer INT(2) NOT NULL, CONSTRAINT pens_in_drawer_range CHECK(pens_in_drawer >= 1 AND pens_in_drawer < 100) );
CHECK()
来保证数据库中的数据是合法的。UNION
操作而不能直接查询一个表。下表包含了ANSI SQL (92, 99 和 2003)、MySQL 3到5.x、PostgreSQL 8.1、MS SQL Server 2000、MS ODBC和Oracle 10.2中的关键字。
A ABORT ABS ABSOLUTE ACCESS ACTION ADA ADD ADMIN AFTER AGGREGATE ALIAS ALL ALLOCATE ALSO ALTER ALWAYS ANALYSE ANALYZE AND ANY ARE ARRAY AS ASC ASENSITIVE ASSERTION ASSIGNMENT ASYMMETRIC AT ATOMIC ATTRIBUTE ATTRIBUTES AUDIT AUTHORIZATION AUTO_INCREMENT AVG AVG_ROW_LENGTH BACKUP BACKWARD BEFORE BEGIN BERNOULLI BETWEEN BIGINT BINARY BIT BIT_LENGTH BITVAR BLOB BOOL BOOLEAN BOTH BREADTH BREAK BROWSE BULK BY C CACHE CALL CALLED CARDINALITY CASCADE CASCADED CASE CAST CATALOG CATALOG_NAME CEIL CEILING CHAIN CHANGE CHAR CHAR_LENGTH CHARACTER CHARACTER_LENGTH CHARACTER_SET_CATALOG CHARACTER_SET_NAME CHARACTER_SET_SCHEMA CHARACTERISTICS CHARACTERS CHECK CHECKED CHECKPOINT CHECKSUM CLASS CLASS_ORIGIN CLOB CLOSE CLUSTER CLUSTERED COALESCE COBOL COLLATE COLLATION COLLATION_CATALOG COLLATION_NAME COLLATION_SCHEMA COLLECT COLUMN COLUMN_NAME COLUMNS COMMAND_FUNCTION COMMAND_FUNCTION_CODE COMMENT COMMIT COMMITTED COMPLETION COMPRESS COMPUTE CONDITION CONDITION_NUMBER CONNECT CONNECTION CONNECTION_NAME CONSTRAINT CONSTRAINT_CATALOG CONSTRAINT_NAME CONSTRAINT_SCHEMA CONSTRAINTS CONSTRUCTOR CONTAINS CONTAINSTABLE CONTINUE CONVERSION CONVERT COPY CORR CORRESPONDING COUNT COVAR_POP COVAR_SAMP CREATE CREATEDB CREATEROLE CREATEUSER CROSS CSV CUBE CUME_DIST CURRENT CURRENT_DATE CURRENT_DEFAULT_TRANSFORM_GROUP CURRENT_PATH CURRENT_ROLE CURRENT_TIME CURRENT_TIMESTAMP CURRENT_TRANSFORM_GROUP_FOR_TYPE CURRENT_USER CURSOR CURSOR_NAME CYCLE DATA DATABASE DATABASES DATE DATETIME DATETIME_INTERVAL_CODE DATETIME_INTERVAL_PRECISION DAY DAY_HOUR DAY_MICROSECOND DAY_MINUTE DAY_SECOND DAYOFMONTH DAYOFWEEK DAYOFYEAR DBCC DEALLOCATE DEC DECIMAL DECLARE DEFAULT DEFAULTS DEFERRABLE DEFERRED DEFINED DEFINER DEGREE DELAY_KEY_WRITE DELAYED DELETE DELIMITER DELIMITERS DENSE_RANK DENY DEPTH DEREF DERIVED DESC DESCRIBE DESCRIPTOR DESTROY DESTRUCTOR DETERMINISTIC DIAGNOSTICS DICTIONARY DISABLE DISCONNECT DISK DISPATCH DISTINCT DISTINCTROW DISTRIBUTED DIV DO DOMAIN DOUBLE DROP DUAL DUMMY DUMP DYNAMIC DYNAMIC_FUNCTION DYNAMIC_FUNCTION_CODE EACH ELEMENT ELSE ELSEIF ENABLE ENCLOSED ENCODING ENCRYPTED END END-EXEC ENUM EQUALS ERRLVL ESCAPE ESCAPED EVERY EXCEPT EXCEPTION EXCLUDE EXCLUDING EXCLUSIVE EXEC EXECUTE EXISTING EXISTS EXIT EXP EXPLAIN EXTERNAL EXTRACT FALSE FETCH FIELDS FILE FILLFACTOR FILTER FINAL FIRST FLOAT FLOAT4 FLOAT8 FLOOR FLUSH FOLLOWING FOR FORCE FOREIGN FORTRAN FORWARD FOUND FREE FREETEXT FREETEXTTABLE FREEZE FROM FULL FULLTEXT FUNCTION FUSION G GENERAL GENERATED GET GLOBAL GO GOTO GRANT GRANTED GRANTS GREATEST GROUP GROUPING HANDLER HAVING HEADER HEAP HIERARCHY HIGH_PRIORITY HOLD HOLDLOCK HOST HOSTS HOUR HOUR_MICROSECOND HOUR_MINUTE HOUR_SECOND IDENTIFIED IDENTITY IDENTITY_INSERT IDENTITYCOL IF IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLEMENTATION IMPLICIT IN INCLUDE INCLUDING INCREMENT INDEX INDICATOR INFILE INFIX INHERIT INHERITS INITIAL INITIALIZE INITIALLY INNER INOUT INPUT INSENSITIVE INSERT INSERT_ID INSTANCE INSTANTIABLE INSTEAD INT INT1 INT2 INT3 INT4 INT8 INTEGER INTERSECT INTERSECTION INTERVAL INTO INVOKER IS ISAM ISNULL ISOLATION ITERATE JOIN K KEY KEY_MEMBER KEY_TYPE KEYS KILL LANCOMPILER LANGUAGE LARGE LAST LAST_INSERT_ID LATERAL LEADING LEAST LEAVE LEFT LENGTH LESS LEVEL LIKE LIMIT LINENO LINES LISTEN LN LOAD LOCAL LOCALTIME LOCALTIMESTAMP LOCATION LOCATOR LOCK LOGIN LOGS LONG LONGBLOB LONGTEXT LOOP LOW_PRIORITY LOWER M MAP MATCH MATCHED MAX MAX_ROWS MAXEXTENTS MAXVALUE MEDIUMBLOB MEDIUMINT MEDIUMTEXT MEMBER MERGE MESSAGE_LENGTH MESSAGE_OCTET_LENGTH MESSAGE_TEXT METHOD MIDDLEINT MIN MIN_ROWS MINUS MINUTE MINUTE_MICROSECOND MINUTE_SECOND MINVALUE MLSLABEL MOD MODE MODIFIES MODIFY MODULE MONTH MONTHNAME MORE MOVE MULTISET MUMPS MYISAM NAME NAMES NATIONAL NATURAL NCHAR NCLOB NESTING NEW NEXT NO NO_WRITE_TO_BINLOG NOAUDIT NOCHECK NOCOMPRESS NOCREATEDB NOCREATEROLE NOCREATEUSER NOINHERIT NOLOGIN NONCLUSTERED NONE NORMALIZE NORMALIZED NOSUPERUSER NOT NOTHING NOTIFY NOTNULL NOWAIT NULL NULLABLE NULLIF NULLS NUMBER NUMERIC OBJECT OCTET_LENGTH OCTETS OF OFF OFFLINE OFFSET OFFSETS OIDS OLD ON ONLINE ONLY OPEN OPENDATASOURCE OPENQUERY OPENROWSET OPENXML OPERATION OPERATOR OPTIMIZE OPTION OPTIONALLY OPTIONS OR ORDER ORDERING ORDINALITY OTHERS OUT OUTER OUTFILE OUTPUT OVER OVERLAPS OVERLAY OVERRIDING OWNER PACK_KEYS PAD PARAMETER PARAMETER_MODE PARAMETER_NAME PARAMETER_ORDINAL_POSITION PARAMETER_SPECIFIC_CATALOG PARAMETER_SPECIFIC_NAME PARAMETER_SPECIFIC_SCHEMA PARAMETERS PARTIAL PARTITION PASCAL PASSWORD PATH PCTFREE PERCENT PERCENT_RANK PERCENTILE_CONT PERCENTILE_DISC PLACING PLAN PLI POSITION POSTFIX POWER PRECEDING PRECISION PREFIX PREORDER PREPARE PREPARED PRESERVE PRIMARY PRINT PRIOR PRIVILEGES PROC PROCEDURAL PROCEDURE PROCESS PROCESSLIST PUBLIC PURGE QUOTE RAID0 RAISERROR RANGE RANK RAW READ READS READTEXT REAL RECHECK RECONFIGURE RECURSIVE REF REFERENCES REFERENCING REGEXP REGR_AVGX REGR_AVGY REGR_COUNT REGR_INTERCEPT REGR_R2 REGR_SLOPE REGR_SXX REGR_SXY REGR_SYY REINDEX RELATIVE RELEASE RELOAD RENAME REPEAT REPEATABLE REPLACE REPLICATION REQUIRE RESET RESIGNAL RESOURCE RESTART RESTORE RESTRICT RESULT RETURN RETURNED_CARDINALITY RETURNED_LENGTH RETURNED_OCTET_LENGTH RETURNED_SQLSTATE RETURNS REVOKE RIGHT RLIKE ROLE ROLLBACK ROLLUP ROUTINE ROUTINE_CATALOG ROUTINE_NAME ROUTINE_SCHEMA ROW ROW_COUNT ROW_NUMBER ROWCOUNT ROWGUIDCOL ROWID ROWNUM ROWS RULE SAVE SAVEPOINT SCALE SCHEMA SCHEMA_NAME SCHEMAS SCOPE SCOPE_CATALOG SCOPE_NAME SCOPE_SCHEMA SCROLL SEARCH SECOND SECOND_MICROSECOND SECTION SECURITY SELECT SELF SENSITIVE SEPARATOR SEQUENCE SERIALIZABLE SERVER_NAME SESSION SESSION_USER SET SETOF SETS SETUSER SHARE SHOW SHUTDOWN SIGNAL SIMILAR SIMPLE SIZE SMALLINT SOME SONAME SOURCE SPACE SPATIAL SPECIFIC SPECIFIC_NAME SPECIFICTYPE SQL SQL_BIG_RESULT SQL_BIG_SELECTS SQL_BIG_TABLES SQL_CALC_FOUND_ROWS SQL_LOG_OFF SQL_LOG_UPDATE SQL_LOW_PRIORITY_UPDATES SQL_SELECT_LIMIT SQL_SMALL_RESULT SQL_WARNINGS SQLCA SQLCODE SQLERROR SQLEXCEPTION SQLSTATE SQLWARNING SQRT SSL STABLE START STARTING STATE STATEMENT STATIC STATISTICS STATUS STDDEV_POP STDDEV_SAMP STDIN STDOUT STORAGE STRAIGHT_JOIN STRICT STRING STRUCTURE STYLE SUBCLASS_ORIGIN SUBLIST SUBMULTISET SUBSTRING SUCCESSFUL SUM SUPERUSER SYMMETRIC SYNONYM SYSDATE SYSID SYSTEM SYSTEM_USER TABLE TABLE_NAME TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TERMINATE TERMINATED TEXT TEXTSIZE THAN THEN TIES TIME TIMESTAMP TIMEZONE_HOUR TIMEZONE_MINUTE TINYBLOB TINYINT TINYTEXT TO TOAST TOP TOP_LEVEL_COUNT TRAILING TRAN TRANSACTION TRANSACTION_ACTIVE TRANSACTIONS_COMMITTED TRANSACTIONS_ROLLED_BACK TRANSFORM TRANSFORMS TRANSLATE TRANSLATION TREAT TRIGGER TRIGGER_CATALOG TRIGGER_NAME TRIGGER_SCHEMA TRIM TRUE TRUNCATE TRUSTED TSEQUAL TYPE UESCAPE UID UNBOUNDED UNCOMMITTED UNDER UNDO UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOCK UNNAMED UNNEST UNSIGNED UNTIL UPDATE UPDATETEXT UPPER USAGE USE USER USER_DEFINED_TYPE_CATALOG USER_DEFINED_TYPE_CODE USER_DEFINED_TYPE_NAME USER_DEFINED_TYPE_SCHEMA USING UTC_DATE UTC_TIME UTC_TIMESTAMP VACUUM VALID VALIDATE VALIDATOR VALUE VALUES VAR_POP VAR_SAMP VARBINARY VARCHAR VARCHAR2 VARCHARACTER VARIABLE VARIABLES VARYING VERBOSE VIEW VOLATILE WAITFOR WHEN WHENEVER WHERE WHILE WIDTH_BUCKET WINDOW WITH WITHIN WITHOUT WORK WRITE WRITETEXT X509 XOR YEAR YEAR_MONTH ZEROFILL ZONE